functions for Lumer's Hardy spaces (L h) 2 (Ω) on arbitrary domains Ω: If a real-valued
harmonic function U∈(L h) 2 (Ω) has a harmonic conjugate V on Ω (ie, a real-valued
harmonic function such that U+ iV is analytic on Ω), then U+ iV also belongs to (L h) 2 (Ω),
and for the normalized conjugate we have the norm estimate|| U+ i V||(L h) 2 (Ω)≤ 2|| U||(L
h) 2 (Ω), with the best possible constant.